Substrate And A Method Of Manufacturing A Substrate

ABSTRACT

Known catalytic converters consist of a ceramic honeycomb monolith substrate and a platinum group metal (PGM) catalytically active coating. 
     A catalytic convertor comprising a substrate body ( 100 ) arranged within the catalytic convertor such that a principal flow of fluid through the catalytic convertor flows along a surface ( 101 ) of the substrate body, wherein said surface ( 101 ) has a plurality of openings ( 210 ) to micro-channels that extend away from said surface ( 101 ); and at least a portion of the surface ( 101 ) of the substrate body ( 100 ) comprises a catalytically active material, wherein the substrate body ( 100 ) is in the form of: a pellet; a sheet; solid elongate bodies; solid rods; a solid body having a plurality of bores; a non-tubular elongate body; a non-hollow body; a sheet curved in the form or a spiral; or a combination thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 14/917,221 filed Mar. 7, 2016 which is the US National phase of PCTApplication No. PCT/GB2014/052698 filed 5 Sep. 2014 which claimspriority to British Application No. 1315841.5 filed 5 Sep. 2013, each ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Known catalytic converters consist of a ceramic honeycomb monolithsubstrate and a platinum group metal (PGM) catalytically active coating.

The effectiveness of this arrangement on exhaust gases is determined bythe geometric surface area of the ceramic honeycomb monolith substrate,which is limited by its effect on the pressure drop as the flow ofexhaust gas passes the substrate; the conventional approach toincreasing surface area is to provide more passages through the monolithsubstrate, but this requires narrower passages.

The maximum geometric surface area of a monolith substrate achieved todate is a figure approaching 5000 m²/m for automotive applications.

It is an object of the present invention to provide an improvedsubstrate for a catalytic converter, having a high geometric surfacearea and offering beneficial flow dynamics.

Hollow fibre membranes have been used in the following papers; Wang etal (2009), Industrial & Chemical Engineering Research 48, 510; Tan etal, Preparation and characterisation of inorganic hollow fibremembranes, J Membr Sci, 2001, 188: 87-95; Preparation of LSCF ceramichollow fibre membranes for oxygen production by aphase-inversion/sintering technique. Ind Eng Chem Res, 2005, 44: 61-66;Yttria stabilised zirconia hollow fiber membranes. J Am Ceram Soc 2006,89: 1156-1159 and A phase inversion/sintering process to fabricatenickel/yttria-established zirconia hollow fibers as the anode supportfor micro-tubular solid oxide fuel cells, J Power Sources, 2008, 183;14-19. In these applications, the oxygen permeability/conductivity ofthe tubes are of great benefit.

BRIEF SUMMARY OF THE INVENTION

The inventors have discovered that the material from which the hollowfibre membranes are manufactured provides a large surface area that canbe advantageous in other applications.

According to the invention, there are provided catalytic convertors andmethods of manufacture of catalytic convertor substrates as defined bythe appended claims.

Embodiments of catalytic convertors in accordance with the inventioncomprise a substrate body having a surface arranged within the catalyticconvertor such that a principal flow of fluid through the catalyticconvertor flows along a surface of the substrate body. The principalflow of fluid is the flow of the bulk of fluid as it passes through thecatalytic convertor. In addition to the principal flow of fluid, theremay be additional eddies of fluid. However, the eddies are not to beconsidered part of the principal flow.

The principal flow of fluid through the catalytic convertor flows alonga surface of the substrate body such that it travels in a directionsubstantially parallel to said surface and in contact therewith.

For example, the catalytic convertor may comprise a housing having aninlet and an outlet, which houses the substrate body. The principal flowwill be from the inlet to the outlet. A portion of the principal flowwill be along the surface of the substrate body.

The catalytic convertor substrate may comprise one or more substratebodies. A co-pending application GB1209155.9, the full disclosure ofwhich is incorporated herein by reference, has been directed to themanufacture of tubular substrate bodies by extrusion. The presentapplication describes a method of manufacturing a larger variety ofsubstrate geometries and is not therefore limited to simple extrudedshapes.

The present application is thus directed to forms of substrate geometryother than the tubular form described in GB1209155.9. That is, thecatalytic convertor substrate does not comprise one or moremicro-structured tubes.

Such geometries may include one or more or combinations of: pellets;sheets; solid rods; a solid body having a plurality of bores;non-tubular bodies; solid/non-hollow bodies; or a curved sheet in theform of a spiral (for example, a sheet wound to form a spiral incross-section having a gap between each roll of the spiral).

Preferably, a substrate body is provided in the form of a sheet with twomajor planar surfaces, which may be flat or curved. The sheet may have aconstant thickness perpendicular to its major surfaces, or its thicknessmay vary. The sheet may be provided with textured major surfaces and/orhave surface structures protruding from its major surfaces.

The catalytic convertor substrate of the embodiments described hereincan have such a large surface area that optionally less catalyst isrequired for high performance.

As such, it is not necessary for the entire substrate body to be coated.Preferably, at least a portion of the substrate body has a coating ofcatalytically active material.

However, alternative embodiments are considered in which the substratebody itself comprises a catalytically active material. This can beachieved in the method described below by including a catalyticallyactive material in the suspension that is shaped (by moulding orextruding) to form a green body.

Preferably, the substrate is coated with a catalytically active coating,such as a washcoat.

Preferably, the micro-structured substrate is ceramic. Themicro-channels may terminate within the substrate or extend from onesurface to another surface.

The micro-structured substrate may be fabricated using a combined phaseinversion and sintering technique described below. Advantageously, thisallows the choice of materials to be based on factors that improve themechanical, thermal and chemical properties of the substrate and improvethe compatibility with the catalytically active material.

In a preferred embodiment the micro-channels have an entrance diameterof 5 μm to 200 μm.

If the substrate is formed as a sheet, the micro-channels preferablyextend at least 30% of the sheet thickness. More preferably, themicro-channels extend at least 80% of the sheet thickness.

A catalytically active coating may be applied to some or all of thesubstrate. In some embodiments, the catalytically active coating maycompletely cover the substrate. If the substrate is formed as a sheet,the catalytically active coating may completely cover one or both of themajor surfaces of the substrate sheet. The coating will not obstruct theopenings of the micro-channels, but will coat the inner surface thereof.

In a preferred embodiment the catalytically active material comprises aprecious metal. However, the GSA provided by the micro-structuredsubstrate can be large enough that only a small quantity of catalyst isrequired.

In a preferred embodiment the precious metal is palladium or a platinumgroup metal.

The substrates described below can be prepared in a cost effective andefficient way. Using the phase inversion and sintering technique,substrates can be prepared from a wide range of materials. Moreover, theformation mechanism for high GSA micro-channels is independent ofmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show how the samemay be put into effect, reference will now be made, by way of exampleonly, to the accompanying drawings in which:

FIGS. 1A-1D show a method of manufacturing a catalytic convertorsubstrate;

FIGS. 2A-2C show simplified examples of catalytic convertors formedusing the method of FIGS. 1A-1D;

FIGS. 3A-3G show surface features that can be formed using the method ofFIGS. 1A-1D;

FIG. 4 shows a cross-section through a substrate formed using the methodof FIGS. 1A-1D; and

FIG. 5 shows an example of a method of manufacturing a substrate.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A to 1D show a first embodiment of a method of manufacturing acatalytic convertor substrate.

As can be seen in FIG. 1A, the method comprises forming a suspension 10and introducing the suspension into a mould 20.

The suspension 10 may contain a substrate material in particulate formand a polymer in a first solvent. In some embodiments the suspension 10may also contain a catalytically active material.

Preferably, the substrate material may comprise one or more of: aceramic; cordierite; zirconia; yttrium-stabilised zirconia; titania;silicon carbide; clay; alumina; stainless steel, FeCr alloys; alloys ofiron; alloys of aluminium; aluminium titanate; or sintered metals.

Preferably, the polymer may comprise one or more of: polyether sulfone;polysulphone; cellulose and its derivatives; polyetherimide; polyimideand its derivatives; PVDF.

Preferably, the first solvent may comprise one or more of: dipolaraprotic solvents; N-methyl-2-pyrrolidone; or dimethyl sulfoxide.

The mould 20 can have any shape. Preferably, the mould 20 is in the formof a tray, so that the suspension 10 when introduced to the mould 20forms a sheet.

A mould 20 having a constant thickness perpendicular to its majorsurfaces is envisaged. However, as shown in FIG. 1, the mould 20 may beshaped and/or orientated so that the suspension 10 when introduced tothe mould 20 forms a sheet with a thickness that increases across itswidth/length.

As can be seen in FIG. 1B, the method comprises contacting thesuspension 10 in the mould 20 with a second solvent 40.

Preferably, the first solvent is miscible with the second solvent 40.

This may be done by immersing the mould 20 and suspension 10 in a bath30 of the second solvent 40. The second solvent 40 may displace some orall of the first solvent in the suspension 10. Optionally, the fluid inthe bath 30 (which may after a period include a mixture of first andsecond solvents) may be replaced periodically or at a constant flow rate(for example, to preserve the concentration of the second solvent).

The displacement of some or all of the first solvent by contacting thesuspension 10 with a second solvent 40 may remove at least some of thefirst solvent from the suspension 10 to thereby form a green body 15formed of the substrate material and the polymer.

When the suspension 10 contacts the second solvent 40, at least some ofthe first solvent will leave the suspension 10 via its exposed surface.In doing so, it forms micro-channels in the suspension 10. (such asthose described with reference to FIG. 4). The micro-channels canpenetrate a large distance through the substrate, but it has beendiscovered that they will not form openings in the surfaces of thesubstrate contacting the mould 20.

The green body 15 will have formed therein micro-channels (describedbelow), which are created by the egress of the first solvent.

As shown in FIG. 1C, the method may comprise removing the mould 20 fromthe second solvent 40. This may be done after a period of time (forexample, 48 hours). The green body 15 can then be removed from the mould20.

The micro-channels formed by the contact between the second solvent 40and the suspension 10 are at the surface of the suspension 10 that isexposed. The micro-channels will penetrate the green body 15 to close tothe opposite side of the green body 15.

As depicted in FIG. 1D by arrows 55, the method may comprise removing atleast a portion of a surface layer of the green body 15 from one or moreof the sides of the green body 15 that contacted the mould 20.

When the mould 20 is, for example, a tray, the green body 15 is in theform of a sheet in which a first major surface of the sheet contactedthe second solvent 40, while a second major surface of the sheet didnot. The method may comprise removing at least a portion of the secondmajor surface layer of said green body 15. Such a method would result ina substrate sheet having openings to micro-channels on both majorsurfaces.

The inventors have also discovered that the micro-channels resultingfrom this method may be tapered so as to have a greater width at agreater depth. Thus a larger opening can be obtained by removing asurface layer having smaller openings at the first surface of the greenbody 15.

Therefore, as depicted in FIG. 1D by arrow 65, the method mayadvantageously also comprise removing at least a portion of a surfacelayer of the green body 15 from one or more of the sides of the greenbody 15 that were exposed to the second solvent 40.

When the mould 20 is, for example, a tray, the green body 15 is in theform of a sheet in which a first major surface of the sheet contactedthe second solvent 40, while a second major surface of the sheet didnot. The method may additionally comprise removing at least a portion ofthe first major surface layer of said green body 15.

The resulting green body 15 may then be sintered to form a finalsubstrate body 100.

At least a portion of the substrate body 100 may then be coated with acatalytically active coating.

Possible ways of carrying out the step of removing at least a portion ofa surface layer may include: removing at least a portion of a surfacelayer by applying heat; removing at least a portion of a surface layerwith a blade; removing at least a portion of a surface layer with anabrasive; sanding at least a portion of the surface of the green body;contacting the surface of the green body with a solvent, water, amixture of solvents, an acidic solution, or a basic solution.

Preferably, removing at least a portion of a surface layer can comprisethermolysing at least a portion of the surface of the green body. Thethermolysed surface portion will simply fall away from the green body.

Alternatively, or in addition, it may be possible to remove at least aportion of a surface layer after sintering. For example, by applying anabrasive; sanding at least a portion of the surface of the sinteredbody; or contacting the surface of the sintered body with acidicsolution or alkaline solution.

Advantageously, the mould 20 may be shaped such that the substrate body100 formed by the above process has provided on at least a portion ofits surface one or more of: protrusions, surface textures, ridges, andother structures for modifying the flow of fluid over the surface.

As shown in FIG. 4, the surface 101 of a substrate 100 manufacturedusing the above method comprises a plurality of micro-channel openings210 (these may be substantially uniform over the surface) which extendas micro-channels 200 to a depth d, which may be slightly less than thethickness of the substrate 100. Owing to the direction in which thefirst solvent leaves the suspension 10, openings 210 are formed in theexposed side of the substrate 100.

The diameter of the openings 210 of the micro-channel 200 is preferablyfrom 5 μm to 200 μm. As the micro-channels 200 terminate inside thesubstrate 100, a skin of solid substrate 100 may be provided on aportion of the outer surface 102 of the substrate 100. Preferably, themicro-channels 200 may extend up to 95% of the thickness t of thesubstrate 100.

A catalytically active coating may be deposited on the surfaces 101, 102of the substrate 100. Advantageously, the micro-channels 200 provide agreater surface area for the coating to contact with the a fluid flowingover the surface of the substrate 100.

FIG. 2A shows a simplified example of a catalytic convertor. In thisexample, two substrate bodies 100 are provided within a housing 110. Thesubstrate bodies 100 are provided in the form of sheets having a greaterthickness at the downstream end of the catalytic convertor than at theupstream end of the catalytic convertor (the flow of exhaust gas isdenoted by arrows 99). Thus, the substrate sheets 100 are tapered (thisis shown in an exaggerated way in FIG. 2A). This structure can be easilymanufactured by appropriately shaping the mould 20 used in the mouldingstep described above.

FIG. 2B shows a further simplified example of a catalytic convertor. Inthis example, a plurality of substrate bodies 100 in sheet-form areprovided within a housing 110. The plurality of substrate bodies areseparated by spacers 120. For example, one spacer 120 may be provided ineach corner of a substrate sheet 100.

Preferably, the spacers will separate the sheets by a distance of fromone to three times the thickness of the sheets. Preferably, the sheetsare separated by double the sheet thickness.

FIG. 2C shows a further simplified example of a catalytic convertorsimilar to the FIG. 2B example. In this example, the spacers 120 areformed integrally with the substrate sheet 100. This structure can beeasily manufactured by appropriately shaping the mould 20 used in themoulding step described above.

Substrates having advantageous surface features such as those shown inFIGS. 3A to 3G may be manufactured by appropriately shaping the mould20. While substrates in the form of a flat sheet of constant thicknessare shown in FIG. 3, the surface features shown may be provided on thesurface of any shape of substrate body by an appropriately shaped mould.

FIG. 3A shows an example of a substrate body 100 having a plurality ofspacers 120 formed on a major surface thereof.

Advantageously, a first substrate body 100 having a plurality of spacers120 may be joined to a second substrate body 100 by placing the firstsubstrate body 100 in contact with the second substrate body 100 priorto the above-described sintering step. The active of sintering can jointhe two first and second bodies 100 together to form a larger substrate.

Optionally, an additional adhesive may be provided between the twosubstrate bodies 100 prior to sintering in order to aid the adherence ofone to the other. The adhesive may be a small quantity of the suspension10.

In addition to shaping the mould 20 to provide structural features toaid construction of a catalytic convertor from one or more substrates100, the mould 20 can be shaped to provide structural features that canmodify the flow of a fluid (e.g. exhaust gas) over the surface of thesubstrate 100. It should however be noted that the principal directionof the flow will be unchanged by such flow modification features, whichmay only influence the flow locally.

FIG. 3B shows an example of a substrate body 100 having a plurality ofridges 130 formed on a major surface thereof. The ridges 130 can beconfigured so that a flow across the major surface becomes turbulent.

As shown in FIG. 3C, the ridges 130 may be formed with a varying heighth1, h2, h3 across the length of the substrate 100.

As shown in plan view in FIG. 3D, a plurality of protrusions 140 may beprovided on the surface of the substrate 100. The protrusions 140 maypartially redirect at least a portion of the flow of a fluid across thesurface of the substrate 100 (as depicted by the dashed arrows in thefigure).

The protrusions 140 may be generally triangular in cross-section (across-section parallel to the surface of the substrate).

As shown in plan view in FIG. 3E, one or more ridges 150 may beprovided. In contrast to the ridges 130, which are preferably notparallel with the principal flow direction (and, most preferably,generally perpendicular to the principal flow direction), ridges 150 mayextend generally in the principal flow direction (depicted by the dashedarrow in the figure).

Optionally, the ridges 150 are not straight. For example, the ridges 150shown in FIG. 3E are wavy. Similarly, ridges 130 may be wavy.

As shown in plan view in FIG. 3F, one or more ridges 150 may benon-continuous. For example, the ridges 150 may be provided with gapsthrough which a portion of the flow of a fluid may be redirected.Similarly, ridges 130 may be non-continuous.

As shown in plan view in FIG. 3G, one or more ridges 150 may be providedwith protrusions for creating eddies in the flow. Similarly, ridges 130may have protrusions.

In general terms, the substrate 100 may comprise surface textures orflow modification structures over a portion of its surface. Thecharacteristics of the surface textures or flow modification structuresmay vary across the surface.

If structural features 120, 130 are required on either side of asubstrate body 100, then two complementary substrates 100 may be formedsuch that each has at least one planar surface and the structuralfeatures 120, 130 formed on other surfaces. The two planar surfaces maybe joined prior to the sintering step.

Although the above description is focussed on the use of moulds forshaping the suspension 10 to form a green body, it is possible toextrude the suspension to form an elongate substrate body. Preferably,the suspension to is extruded form a non-tubular elongate substratebody.

The elongate substrate body can have any cross-sectional shape. Forexample, the substrate body may be a cylindrical rod. A catalyticconvertor may comprise a plurality of such rods.

Such a method of manufacturing a substrate comprises: providing asuspension containing a substrate material in particulate form and apolymer in a first solvent (the suspension may comprise a catalyticallyactive material); extruding the suspension; contacting the extrudedsuspension with a second solvent to remove at least some of the firstsolvent from the suspension and thereby form a green body havingmicro-channels from said substrate material and said polymer; removingat least a portion of a surface layer of said green body; and sinteringthe green body.

Since the extruded suspension can be contacted by the second solventover its entire surface because it is not obstructed by a mould,openings will be formed on its surface. However, it is still beneficialin some cases to remove a portion of a surface layer in order toincrease the opening area of the micro-channels. This can be done usingany of the methods described herein.

A further method of manufacturing a catalytic convertor is tomanufacture a catalytic convertor substrate using the methods describedabove, and then to break the sintered body (for example, by crushing ormachining) to form a plurality of substrate pellets.

Owing to the beneficially high geometric surface area of the substrates100 described above, they may be coated at least in part with acatalytically active coating (or be formed with catalytically activematerial) and used in a catalytic convertor.

Such catalytic convertors may be used in fixed applications or invehicles. In particular, such catalytic convertors may be used inautomobiles.

There follows a brief example of the steps of the method set out above.

A flow diagram showing the stages involved in the preparation of asubstrate is shown in FIG. 5. The parameters (A to U) for three examplesare given below.

A dispersant (D) is dissolved in a solvent (C) prior to the addition ofinorganic material (A). This forms a dispersion. In one embodiment, theinorganic material is in the form of a powder with a particledistribution of 1:2:7 (0.01 μm:0.05 μm:1 μm).

The dispersion is rolled/milled. For example, using 20 mm agate ballsmilling for 48 hours with approximately twice as much alumina/agate byweight as dispersion. A polymer binder (B) is added, after which millingmay be continued for up to a further 48 hours.

Preferably, the resulting suspension is transferred to a gas tightreservoir and degassed under vacuum until no bubbles are seen at thesurface.

The suspension is then introduced into a mould 20 or is extruded. Whenmoulding is used, the mould 20 is submerged in a coagulation bathcontaining a non-solvent (K) for the polymer binder. When extrusion isused, the suspension may be extruded directly into the bath. Ifrequired, a different coagulant (I) may be used with a controlled flowrate (J).

The solvent (C) is miscible with the non-solvent (K).

The substrate may be left in the coagulation bath for an extended period(for example, overnight) to allow for completion of phase inversion ofthe polymer binder.

Preferably, the green body 15 is then immersed in an excess of water(e.g. tap water) replaced periodically over a period of 48 hours inorder to remove traces of the solvent (C). Alternatively, a flow ofwater across the green body 15 may be provided.

Finally, the green body 15 is calcined in air with a predeterminedsintering profile (L to P) to yield a ceramic substrate.

The sintering process reduces the size of the substrate. This results ina substrate having the following properties: Thickness (S);Micro-channel length (T); and Micro-channel width (U).

The table below shows the parameters, A to U, for three examples

Param- eter Example 1 Example 2 Example 3 A Yttrium- Aluminium Aluminiumstabilized oxide(60 wt %) oxide(60 wt %) zirconia (44 wt %) B Polyethersulfone Polyether sulfone Polyether sulfone (8 wt %) (6 wt %) (6 wt %) CN-methyl-2- N-methyl-2- Dimethyl pyrrolidone pyrrolidone sulfoxide (33wt %) (34 wt %) (34 wt %) D polyethylene Arlacel P135 Arlacel P135glycol (15 wt %) (0.001 g/m²) (0.001 g/m²) J 12 ml/min 3 ml/min 5 ml/minK water water water L Room temperature Room temperature Room temperatureto 600° C. at to 600° C. at to 600° C. at 2° C./min 2° C./min 2° C./minM Dwell for 2 hours Dwell for 2 hours Dwell for 2 hours N 600 to 1400°C. at 600 to 1450° C. at 600-1450° C. at 5° C./min 5° C./min 5° C./min ODwell for 4 hours Dwell for 4 hours Dwell for 4 hours P 1400° C. to room1450° C. to room 1450° C. to room temperature at temperature attemperature at 5° C./m 5° C./min 5° C./min S 0.3 mm 0.3 mm 0.85 mm T 0.3mm (100% of 0.28 mm (93% of 0.67 mm (78% fibre wall) fibre wall) offibre wall) U 0.02 mm 0.02 mm 0.07 mm

In a further exemplary embodiment, the following method was used:

Arlacel P135 at a concentration of 1.3 wt % was dissolved in NMP/watersolutions (having 95 wt % N-methyl-2-pyrrolidone and 5 wt % water) priorto the addition of aluminium oxide powders (58.7 wt %) at a ratio of1:2:7 (for mean particle sizes 0.01 μm:0.05 μm:1 μm) The dispersion wasrolled/milled with 20 mm agate milling balls with an approximatealumina/agate weight ratio of 2 for 48 hours. Milling was continued fora further 48 hours after the addition of polyether sulfone (6.1 wt %).The suspension was then transferred to a gas tight reservoir anddegassed under vacuum until no bubbles could be seen at the surface.

After degassing, the suspension was introduced into a mould 20 andsubmerged in a coagulation bath containing 120 litres of water (anon-solvent for the polymer).

The substrate was left in the coagulation bath overnight to allow forcompletion of phase inversion. The green body 15 was then immersed in anexcess of tap water which was replaced periodically over a period of 48hours in order to remove traces of NMP. Finally, the green body 15 wascalcined in air (CARBOLITE furnace) to yield a ceramic substrate. Thetemperature was increased from room temperature to 600° C. at a rate of2° C./min and held for 2 hours, then to the target temperature (1200° C.to 1600° C.) at a rate of 5° C./min and held for 4 hours. Thetemperature was then reduced to room temperature at a rate of 5° C./min.

1. A method of manufacturing a substrate having a plurality ofmicro-channels formed therein, the method comprising: providing asuspension containing a substrate material in particulate form and apolymer in a first solvent; introducing the suspension into a mould orextruding the suspension; contacting the suspension with a secondsolvent to remove at least some of the first solvent from the suspensionand thereby form a green body having micro-channels from said substratematerial and said polymer; removing at least a portion of a surfacelayer of said green body; and sintering the green body.
 2. The method ofclaim 1, wherein the step of removing a layer of material comprisesremoving material to uncover openings in the outer surface of the greenbody.
 3. The method of claim 1, wherein the step of removing a layer ofmaterial is carried out using a blade.
 4. The method of claim 1, whereinthe step of removing a layer of material is carried out using anabrasive.
 5. The method of claim 1, wherein the step of removing a layerof material is carried out by sanding.
 6. The method of claim 1, whereinthe mould is shaped such that the green body forms a sheet of material.7. The method of claim 1, wherein the mould is shaped to form a sheet ofmaterial having at least one protrusion extending from a major surfacethereof.
 8. The method of claim 1, wherein the suspension comprises acatalytically active material.
 9. The method of claim 1, furthercomprising coating at least a portion of the substrate with acatalytically active coating.
 10. The method of claim 2, wherein theopenings have widths failing in the range 5 μm to 200 μm.
 11. A methodof manufacturing a substrate having a plurality of micro-channels formedtherein, the method comprising: providing a suspension containing asubstrate material in particulate form and a polymer in a first solvent;introducing the suspension into a mould or extruding the suspension;contacting the suspension with a second solvent to remove at least someof the first solvent from the suspension and thereby form a green bodyhaving micro-channels from said substrate material and said polymer;sintering the green body to form a sintered body; and removing at leasta portion of a surface layer of said sintered body.
 12. The method ofclaim 11, further comprising removing at least a portion of a surfacelayer of said green body.
 13. The method of claim 11, wherein the stepof removing a layer of material comprise removing material to uncover aplurality of micro-channel openings, wherein the openings have diametersfrom 5 μm to 200 μm.
 14. The method of claim 11, wherein the step ofremoving a layer of material is carried out using an abrasive.
 15. Themethod of claim 11, wherein the step of removing a layer of material iscarried out by sanding.
 16. The method of claim 11, wherein the step ofremoving a layer of material is carried out by contact the surface ofthe sintered body with acidic solution or alkaline solution.
 17. Themethod of claim 11, wherein the mould is shaped such that the green bodyforms a sheet of material.
 18. The method of claim 11, wherein the mouldis shaped to form a sheet of material having at least one protrusionextending from a major surface thereof.
 19. The method of claim 11,wherein the suspension comprises a catalytically active material. 20.The method of claim 11, further comprising coating at least a portion ofthe substrate with a catalytically active coating.
 21. A method ofmanufacturing a catalytic convertor substrate comprising the methodclaim 1
 22. A catalytic convertor substrate manufactured according themethod of claim 1.